Rieber U.S. Pat. No. 2,559,227 describes an apparatus for generating high frequency shock waves and comprising a reflector in the form of a truncated ellipsoid having shock waves generated by an electric arc or discharge between two electrodes converging on a first focus of the ellipsoid, thereby serving to destroy a target disposed at the second focus of the ellipsoid lying outside the truncated reflector.
The Reiber electrodes are made of highly conductive material such as copper or brass and are mounted on an insulator which is pivotally supported by a device serving to adjust the gap between the electrodes.
U.S. Pat. No. 3,942,531 describes a similar apparatus in which the liquid is constituted by water.
When using the Rieber apparatus or a similar apparatus, an electric arc or discharge is produced between the electrodes by suddenly discharging a capacitor by closing a high tension switch. In the Rieber apparatus, the circuit between the electrodes includes a capacitor and an associated self-inductor. It has been observed that the capacitor discharge is of the damped oscillating type. In other words, the capacitor discharges and then recharges in the opposite direction to a lower voltage than its initial voltage (which is very high and about 15,000 V to 20,000 V), and then recharges the initial way around, and so on until the charge contained in the capacitor has been lost.
Simultaneously, an electric arc is established between the two electrodes and as a result the associated current is also of the damped oscillating type.
When an electric arc or current is established between the two electrodes, the liquid, and in particular water, is vaporized, thereby generating a pressure wave or shock wave which can be used for destroying a target.
It will be understood, that the quicker the liquid, and in particular water, vaporizes, the stronger the pressure wave and the shorter its rise time.
Thus, in order to vaporize a large quantity of liquid, and in particular water, it is necessary to suddenly deliver a larger amount of energy.
All presently known devices give rise to discharges which are always of the damped oscillating type, which type is shown in FIG. 2aof the present application, and the total energy dissipated over time is shown in accompanying FIG. 2b. These figures are described in greater detail below, and the energy is dissipated progressively over time.
The main object of the present invention is therefore to solve the novel technical problem of delivering suddenly or in a relatively short length of time the major portion of the energy stored by charging the capacitor in the discharge circuit between two electrodes.
Another object of the present invention is to solve the novel technical problem of producing an initial pressure wave which is substantially spherical.
Yet another object of the, present invention is to solve the novel technical problem of reducing electrode wear.
These novel technical problems are solved in satisfactory manner for the first time by the present invention.